黃 忠,王乃興,田 強,李玉葉
(1.云南省化工研究院,昆明 650228;2.中國科學院理化技術研究所,北京 100080)
·科學研究·
超聲波輻射條件下錫(II)催化合成二吲哚基甲烷的方法研究*
黃 忠1*,王乃興2*,田 強1,李玉葉1
(1.云南省化工研究院,昆明 650228;2.中國科學院理化技術研究所,北京 100080)
研究了一種由SnCl2催化合成二吲哚基甲烷的高效方法。引用超聲波輻射作為反應條件,在反應體系中加入當量的催化劑能夠在短時間內合成出二吲哚基甲烷且分離方法簡單易行。合成出的系列二吲哚基甲烷具有一定的光學性質,即在400~600 nm波長范圍內范圍內具有光吸收作用,且在受波長為370 nm光的激發下,會發出波長約為440 nm的紫光。
超聲波輻射;吲哚;二吲哚基甲烷;熒光
眾所周知,二吲哚基甲烷(BIMs)系列化合物擁有廣泛的生物活性而被應用于藥物行業[1]。例如,BIMs能夠增加生物體荷爾蒙和雌性激素分泌和有效地緩解纖維肌痛癥狀[2],BIMs由于具有調節癌癥相關激素代謝產物的功效而能夠有效地預防癌癥[3]。由于BIMs在醫療上具有上述的重要作用,一些文獻報道了BIMs的合成方法[4-14],其可以通過吲哚及其衍生物與醛或酮類化合物在催化劑的作用下發生縮合反應來合成。這些催化劑包括質子酸(例如HCl)[4],路易斯酸(如AuCl3,In(OTf3),ZrCl4)[5]。但是這些合成方法都具有各自的缺點,如反應時間長、催化劑負載量大、催化劑昂貴(如AuCl3,In(OTf3))、產物收率低、反應溫度高和分離方法復雜等。因此有必要尋找一種新的方法克服上述不足。
超聲波輻射在許多有機反應中已經被證明是一種有效的合成技術[15]。與傳統方法相比,此技術具有產率高、反應時間短和反應條件溫和的優點[16]。由文獻可知,絕大部分Lewis酸催化合成BIMs需要超過當量比的催化劑和很長的反應時間[4g,5b,17]。在本研究中,闡述了超聲波輻射條件下,SnCl2在室溫下催化吲哚與醛或酮的縮合反應制備BIMs的新發現。與先前報道的方法相比,本研究的超聲波輻射方法具有催化加負載量小(僅需要當量級的催化劑)、收率高和反應時間短的優點。SnCl2在室溫下催化吲哚與醛或酮的縮合反應制備BIMs的反應式如下:

1.1 試劑與儀器
所用的試劑均為市售分析純試劑。SILG/UV 254型薄層硅膠色譜;X-4型熔點測定儀;Excalibur 3 100(Varian)紅外光譜儀;測定(KBr制片)。Bruker 400 MHz核磁共振譜(TMS作為內標);Bruker Microflex質譜儀;UV-2501PCS型雙通道光譜儀;Shimadzu RF-5301PC型熒光光譜儀。
1.2 實驗步驟
在含有吲哚(1,1 mmol),醛或酮(0.5 mmol)和溶劑(0.5 mL)的體系中加入催化劑(0.5 mmol)。反應體系在超聲波輻射條件下,室溫反應,反應一段時間后反應混合物通過真空過濾以除去催化劑,催化劑使用CH2Cl2(5 mL×3)洗滌,合并濾液。濾液通過真空濃縮后,經柱層析色譜進行分離得到純凈的目標產物(層析介質為硅膠,洗滌劑為乙酸乙酯-石油醚,體積比為1∶3~1∶5)。
1.3 目標產物表征
1)3-((2,4-Dichlorophenyl)(1H-indol-3-yl)methyl)-1H-indole(3a):產率96%;1H NMR(400 MHz,CDCl3)∶6.29(s,1 H),6.59(d,J=1.6 Hz,2H),7.03-7.10(m,3 H),7.15(d,J=8.4 Hz,1H),7.20(t,J=8.0 Hz,2H),7.35(d,J=8.0 Hz,2H),7.39(d,J=8.0 Hz,2H),7.46(d,J=2.0 Hz,1H),7.85(brs,2H,NH);13CNMR(400 MHz,CDCl3):36.4,111.3,117.9,119.6,119.8,122.3,123.9,126.9,127.1,129.4,131.3,132.6,134.7,136.8,140.2;IR:3413,3 055,2 924,2 851,1 587,1 557,1 455,1417,1216,1095,864,797,740 cm-1.EI-MS:理論值:390.069 3;測定值:390.050 9.熔點:107-109℃。
2)3-((1H-indol-3-yl)(4-nitrophenyl)methyl)-1H-indole(3b):產率:80%;1H NMR(400 MHz,CDCl3)∶d=5.60(s,1 H),6.69(d,J=1.7 Hz,2 H),7.03(t,J=7.6 Hz,2 H),7.20(t,J=7.5 Hz,2 H),7.34(d,J=8.0 Hz,2 H),7.39(d,J=8.2 Hz,2 H),7.51(d,J=8.6 Hz,2 H),8.05(br s,2 H,NH),8.14(d,J=8.7 Hz,2 H);IR:3420,3076,3055,2959,2851,1568,1488,1456,1 338,1 093,1 075,742 cm-1.熔點:247-249℃.[6]
3)3-((1H-indol-3-yl)(phenyl)methyl)-1H-indole(3c):產率:93%.1H NMR(400 MHz,CDCl3)∶5.89(s,1 H),6.64(d,J=1.6 Hz,2 H),6.99-7.03(m,2 H),7.15-7.19(m,2 H),7.22(d,J=7.2 Hz,1 H),7.26-7.30(m,2H),7.34-7.36(m,4H),7.39(d,J=7.9 Hz,2H),7.88(br s,2 H,NH);13C NMR(400 MHz,CDCl3):40.3,111.2,119.3,119.7,120.0,122.0,123.8,126.3,127.2,128.3,128.8,136.8,144.2;IR:3415,3055,3027,2959,2925,2 852,1 600,1 492,1 456,1 417,1 336,1 073,1 010,743,701 cm-1.熔點:90-94℃.[6]
4)Methyl4-(di(1H-indol-3-yl)methyl)benzoate(3d):產率:93%.1H NMR(400 MHz,CDCl3)∶4.13(d,J=7.1 Hz,3H),5.94(s,1 H),6.66(d,J=1.6 Hz,2 H),7.01(t,J=7.7 Hz,2 H),7.18(t,J=7.8 Hz,2 H),7.35-7.38(m,4H),7.42(d,J=8.2 Hz,2H),7.95-7.97(m,4SH);13C NMR(400 MHz,CDCl3)∶40.4,52.1,111.3,118.7,119.4,119.8,122.1,123.8,126.9,128.2,128.9,129.7,136.8,149.8,167.5;IR:3 406,3 054,2 950,2 925,2 852,1 704,1 606,1456,1435,1418,1282,1115,762,743,704 cm-1;熔點:118-120℃.[10a]
5)3-((1H-indol-3-yl)(4-methoxyphenyl)methyl)-1H-indole(3e):產率:98%;1H NMR(400 MHz,CDCl3)∶3.79(s,3H),5.85(s,1 H),6.65(s,J=1.5 Hz,2 H),6.82(d,J=8.6 Hz,2 H),7.01(t,J=7.5 Hz,2 H),7.17(t,J=7.6 Hz,2 H),7.25(d,J=8.6 Hz,2H),7.35(d,J=8.2 Hz,2H),7.39(d,J=7.9 Hz,2H),7.89(br s,2 H,NH);13C NMR(400 MHz,CDCl3)∶39.5,55.4,111.1,113.7,119.4,120.1,120.2,122.0,123.7,127.2,129.8,136.4,136.9,158.1;IR:3439,3055,2957,2930,2835,1 608,1 509,1 456,1 417,1 338,1 243,1 091,792,741 cm-1;熔點:200-202℃.[6]
6)3-(Furan-2-yl(1H-indol-3-yl)methyl)-1H-indole(3f):產率:80%;1H NMR(400 MHz,CDCl3)∶5.95(s,1 H),6.06(d,J=2.7 Hz,1 H),6.31(d,J=2.6 Hz,1H),6.86(s,2 H),7.04(t,J=7.5 Hz,2 H),7.18(t,J=7.7 Hz,2 H),7.34-7.36(m,3 H),7.49(d,J=7.9 Hz,2 H),7.92(br s,2 H,NH);IR:3 411,3 120,3 056,2 956,2 923,2 852,1 504,1 456,1 418,1 336,1 217,1 094,1 010,783,742 cm-1;M.P.:>300℃.[4c]
7)3-((4-(Di(1H-indol-3-yl)methyl)phenyl)(1H-indol-3-yl)methyl)-1H-indole(3ga)和3gb:3ga和3gb的產率分別為78%和20%。
3ga:1H NMR(400 MHz,CDCl3):5.80(s,2 H),6.42(s,4 H),7.01(t,J=7.2 Hz,4 H),7.15(t,J=7.2 Hz,4 H),7.24(s,4 H),7.29(d,J=8.0 Hz,4H),7.38(d,J=7.9 Hz,4H),7.58(br s,4 H,NH);IR:3 407,3 054,2 960,2 924,2 848,1 456,1 417,1 336,742 cm-1;熔點:182-184℃.[8b]
3gb:IR:3 399,3 055,2 960,2 924,2 845,1 695,1 602,1 575,1 456,1 417,1 338,1 212,1 094,1 011,785,743 cm-1;熔點:204-206℃([8a]203-204℃)
8)3h:產率:80%.IR:3414,3085,3052,2 932,2 854,1 456,1 415,1 336,1 264,1 242,1 102,1 014,763,741 cm-1;熔點:145-147℃(146-147℃).[7]
9)3-(2-(1H-indol-3-yl)propan-2-yl)-1H-indole:(3i):產率:30%.1H NMR(400 MHz,CDCl3):1.93(s,6 H),6.87-6.91(m,2 H),7.06-7.11(m,4 H),7.32(d,J=8.1 Hz,2 H),7.43(d,J=8.2 Hz,2 H),7.89(br s,2 H,NH);IR:3 412,3 084,3 054,2 964,2 930,2 869,1 487,1 456,1 415,1 334,1 099,1 012,769,741 cm-1;熔點:165-167℃.[10c]
10)3-(1-(1H-indol-3-yl)butyl)-1H-indole(3j):產率:33%.1H NMR(400 MHz,CDCl3):0.97(t,J=7.4 Hz,3 H),1.42-1.48(m,2 H),2.19-2.15(m,2 H),4.49(t,J=7.4 Hz,2 H),6.99(d,J=2.2 Hz,2 H),7.03-7.07(m,2 H),7.14-7.18(m,2 H),7.33(d,J=8.1 Hz,2 H),7.62(d,J=7.9 Hz,2 H),7.86(br s,2 H,NH);IR:3 410,3 078,3 055,2 956,2 925,2 870,1 456,1 417,1 337,1 093,1 011,741 cm-1;熔點:247-249℃.[10d]
2.1 反應條件探索
本文研究了在不同催化劑催化條件下,吲哚與2,4-二氯苯甲醛(2 a)合成BIM(3 a)的反應,反應結果見表1。
由表1看,在無催化劑的條件下,在180 min的反應時間內,3 a的收率少于10%。當用2 d和2 e作為反應底物時,檢測不到相關產物3 d和3 e的生成。當加入當量的Lewis酸作為催化劑時,3 a的收率得到大幅度的提高。在篩選的催化劑中,SnCl2的效果最明顯,在15 min的反應時間內其產率最高,達到了96%。雖然CuBr2催化的反應速度最快,但是其催化反應出大量的副產物造成分離困難,目標產物收率低。Mg(ClO4)2的催化活性很低,在180 min的反應時間內,目標產物的收率僅有45%。此結果說明,催化劑的活性對目標產物的收率具有十分重要的作用。在篩選的催化劑中,SnCl2的催化活性適中,是此類反應最為合適的催化劑。

表1 由吲哚與2,4-二氯苯甲醛制備BIM(3a)反應條件實驗結果Tab.1 Optimization on the conversion of indole and 2,4-dichlorobenzaldehyde to BIM(3a)
2.2 反應介質對反應的影響
在篩選催化劑之后,本研究考察了在SnCl2作為催化劑的條件下,不同的反應介質的溶劑化效應對本反應的影響。本反應在二氯甲烷、甲苯和甲醇中能夠順利的進行并得到目標產物,且收率高。此結果說明SnCl2可以廣泛的適應于極性和非極性溶劑。但是,相比之下SnCl2在二氯甲烷和甲苯中具有更高的催化活性和選擇性??紤]到反應時間,二氯甲烷最為合適。篩選出反應介質之后,研究發現與常規的攪拌相比,超聲波輻射條件下反應的速度提高了16倍。
因此,本研究得出了BIMs制備的最佳條件,即在室溫下通過超聲波輻射,使用二氯甲烷作為反應溶劑,SnCl2作為催化劑。據此前文獻報道,由于許多Lewis酸受反應體系中氮氣捕獲作用而失效,故使用量要多于當量比[4g]。而本研究僅需要當量比的催化劑,故會大幅度降低合成成本。研究認為超聲波輻射能夠有效地排除體系中的氮氣,超聲波輻射帶來的劇烈震動能夠減小反應底物及催化劑與氮氣接觸的幾率,如此便能使此反應暴露在空氣中進行,有效地降低了反應條件。
在篩選的最佳條件下,本研究考察芳香醛、脂肪醛和酮與吲哚的反應,并制備了一系列的BIMs,實驗結果如表2所示。表2結果顯示,芳香醛無論是反應速度或產物收率均高于脂肪醛和酮。在芳香醛的反應中,絕大部分芳香醛能夠順利反應并在短時間內得到高收率的目標產物。芳香醛中的芳環特性對反應速度具有十分重要的作用,即富電子芳環比缺電子芳環需要更長的反應時間。如2b比2c活潑,更容易與吲哚發生反應,同時副反應也更容易發生,造成反應選擇性下降和目標產物的收率較低。TLC檢測顯示,2b比2c擁有更多的無法界定的副產物,并隨著反應時間的延長,副產物的種類也隨著增多。在2e反應中,由于對甲氧基苯基屬于富電子基團,故反應體現了很高的選擇性。盡管2f體現得不夠活潑,但是在超聲波輻射條件下,120 min的反應時間內,其反應收率能夠達到80%。由于2g為二醛,故其反應有兩種反應產物,反應完全時產物為3ga,反應不完全時產物為3gb,其中后者為前者的副產物,二者的總收率為98%。根據實驗結果,芳香醛的反應速度要高于酮,原因是空間位阻效應,很明顯具有兩個取代基的酮的位阻大于只有一個取代基的醛。因此丙酮的轉化率非常低,在120 min反應時間內,目標產物僅有30%。若取代基R1和R2為剛性結構,其空間位阻效應有限,如環己酮(2h)與吲哚的反應產物收率在120 min內達到80%。

表2 吲哚與醛酮反應制備BIMs實驗結果Tab.2 Condensation of indole with various aldehydes and ketones to form BIMs
由于BIMs 3a-e和3ga除了吲哚基之外還具有其他芳環取代基,筆者認為這些BIMs具有一定的光學性質。于是本文還研究了這些化合物在三氯甲烷中的吸收光譜、激發和發射光譜,如表3所示。表3結果顯示,除3b外,其他所有BIMs在400~600 nm的波長范圍內均有吸收作用,當使用370nm的紫外光激發這些化合物時,這些化合物均體現出了熒光效應,其的最大發射峰在440 nm處,即發射紫光。在比較這些化合物的光譜后發現,苯環上的取代基對光學性質的影響很小。3a具有最大的Stokes位移,為28 nm,3c和3ga具有最小的Stokes位移為13 nm。另外,根據紫外-可見吸收光譜的起始吸收帶,可以計算出這些化合物的禁帶寬度約為2.40 eV。此結果表明,這些BIMs可以作為半導體和光學材料研究的潛在對象。

表3 部分BIMs的光學性質Tab.3 Optical properties of some BIMs
探討了一種在室溫下合成BIMs的有效地合成方法。該方法在超聲波輻射條件下進行,具有反應條件溫和、反應時間短、產物收率高、分離簡單和催化劑簡單且使用量較少的優勢。制備的BIMs具有一定的光學性能和滿足半導體的基本條件,可以作為半導體和光學研究的潛在應用材料。
本研究感謝云南省科技創新平臺建設計劃(2015DC008)的支持。
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An Efficient Synthesis of Bis(indolyl)methanes Catalyzed by Sn(Ⅱ)in Ultrasonic Irradiation
HUANG Zhong1*,WANG Nai-xing2*,TIAN Qiang1,LI Yu-ye1
(1.Yunnan Chemical Research Institute,Kunming 650228,China
2.Technical Institute of Physics and Chemistry,Chinese Academy of Sciences,Beijing 100080,China)
An efficient synthesis of bis(indolyl)methanes catalyzed by SnCl2was developed with good yields.The new method in the presence of ultrasonic irradiation is successful with stoichiometric catalyst,short reaction time and very easily isolation procedure.These prepared products have a wide absorption at the region of 400-600 nm when excited by ultraviolet of about 370 nm.Their emission peaks are about 440 nm,indicating that these BIMs emit purple light.
Condensation,ultrasonic irradiation,indole,bis(indolyl)methanes,fluorescence
O621.3
A
1004-275X(2015)05-0001-07
10.3969/j.issn.1004-275X.2015.05.001
*特約稿件
收稿:2015-09-07
云南省科技創新平臺建設計劃(2015DC008)。
黃忠(1983-),男,湖南溆浦人,博士,高級工程師,主要從事有機精細化工產品的研發工作。pifushu@163.com。